Hi, I am quite new to all this. I bought the above charger and had it on a solar panel of 15 watts charging 2 100Ah AGM batteries that are for running a diesel heater in the winter. The batteries sat at 12.2 volts all of the time. I bought a 420 watt solar panel and plugged that in instead, now the batteries charge and seem to be happy at around 13.7 volts.
I understand that it is more efficient to put the batteries in series and charge at 24 volts, easy to do. I would need a DC 24v to 12v convertor for the heater.
My main questions are:
Will the pins on the MPPT for loads still be at 12 volts, or will they also output 24 volts? I use these outputs for charging my 12v head torch and other 12v stuff.
Does it matter that the two agm batteries are different ages? I assume that they will still charge, but perhaps not as well as two identical batteries.
The battery and load terminals in the MPPT are connected together so they have the same voltage. If you go to 24V battery the load terminals will also be 24V.
Your MPPT at 15A output charging at 14V will be limited to 210W so going to 24V will be able to harvest more power, up to 420W, but you will need to buy 24V to 12V DC converter. Would it be cheaper to buy a 30A MPPT and stay at 12V.
Ideally connecting batteries in parallel or series they should be same age. If they are different then in series you need to check the mid point voltage regularly to make sure that they are staying balanced. In parallel, by definition they both have the same voltage.
Thank you, perhaps I would be better just buying a single new Lipo battery, but you have answered my main question.
There is a 5 volts above the battery voltage from your solar panels to start the MPPTt. After start you need 1 volts above the battery voltage.
For a 12 volt battery of about 13.5 volts that means you need 19 volts from the panels. For a 24 volt battery which would rest at about 27 volts, you’d need a solar panel array of at lest 32 volts.
I seem to have the volts coming from the 420 watt panel, usually sits well above 32. Two screen shots, one shows the history over the last few days and the other the output now on this overcast misty morning.
As you can see, I have made up a little lead from my MPPT (no bluetooth) to connect to my phone and try to understand more. I was quite amazed when it worked. 